An electron localization function investigation of bonding in some simple four-coordinate nitrogen and phosphorus compounds

The bonding in some simple four-coordinate species involving nitrogen and p hosphorus has been studied by the electron localization function (ELF) appr oach and compared to that in their conventionally singly and doubly bonded counterparts. Despite evidence suggesting the presence of a conventional mu ltiple bond in certain cases of the four-coordinate species, the ELF study shows this not to be the case. Rather the situation is better pictured as, for example, in the case of H3PCH2 as [GRAPHICS] where both ionic and covalent interactions are present, a type of bond we t erm cov-ionic. While the ionic interaction is generally strong, the covalen t part can be weak, as in the case of the four-coordinate nitrogen compound s, or strong as in the case of the four-coordinate phosphorus species. The quantum mechanically determined properties of the cov-ionic bonded compound s ave consistent with this picture. (C) 2000 John Wiley & Sons, Inc.